1. Field of the Invention
This invention relates to an ultrasonic vibrator which is suitable for transporting a small flow rate of powder.
2. Description of the Related Art
It is well known in a gazette of Japanese Patent Laid-Open No. Hei 7-33228 to provide a powder transporting device comprising a transporting cylinder of which upstream end is connected to an outlet of a powder hopper to form a power transporting passage and an ultrasonic driving device (an ultrasonic vibrator) using a bolt fastened Langevin type vibrator and applying an ultrasonic vibration showing an elliptical orbit to powder kept in the transporting passage (hereinafter called as a first prior art).
In this type of powder transporting device, the powder hopper and the ultrasonic vibrator are supported by a supporting member such as a frame or the like.
The ultrasonic vibrator is made such that upper and lower metallic blocks having a substantial circular cylinder are connected by metallic bolts. Then, a ring-like electrode, a first ring-like piezo-electric element, a pair of ring-like divided electrodes and a second ring-like piezo-electric element are held in sequence from a lower stage between both metallic blocks while being fitted to the bolts.
In addition, it is also well known in the art to provide an ultrasonic vibrator by a gazette of Japanese Patent Laid-Open No. Hei 7-155687 that both blocks are connected by a connecting rod under a state in which the ring-like piezo-electric elements are being held between a pair of blocks, a periodically varying voltage is applied to the piezo-electric elements to generate a complex vibration composed of a vertical vibration and a flex vibration, wherein the connecting rod is formed with an axial hole therein, a fixing shaft positioned with a certain clearance in respect to an inner wall of the hole is inserted into the hole, and an inserting end of the fixing shaft is fixed to the ultrasonic element at a section of a complex vibration of the ultrasonic vibrator (hereinafter called as a second prior art).
In this second prior art, the electrodes for applying a periodically varying voltage to the piezo-electric elements are composed of divided electrodes which are equally divided into four segments in a circumferential direction of the ring-like piezo-electric elements, any one of the four divided electrodes is selectively used to enable a vibrating plane of the flex vibration to be changed over and it is supported at a location where it becomes a section of complex vibration in common irrespective of any type of vibrating plane of the flex vibration. Accordingly, a resonant phenomenon is always generated irrespective of the vibrating plane to enable a stable ultrasonic vibration to be attained.
In the aforesaid first prior art, since an ultrasonic vibration showing an elliptical orbit is applied to powder through an elliptical motion of an extremity end of a horn part formed at an upper end of an upper metallic block, it can be provided that a lower end of a lower metallic block is fixed to the supporting member in order to support the ultrasonic vibrator by the supporting member such as a frame or the like.
Although no description is found in the aforesaid first prior art about a practical supporting structure for the ultrasonic vibrator, there were some problems that supporting of a lower end of the lower metallic block may cause a vibrating energy leaked from the ultrasonic vibrator through the supporting part to be increased, a high amount of driving electrical power is required for applying an elliptical orbit of desired value and an efficiency of the ultrasonic vibrator is decreased.
In addition, in the aforesaid second prior art, the electrode was divided electrodes which are equally divided into four segments in a circumferential direction, wherein a circumferential angle of one electrode is about 90.degree., resulting in that the driving electrical power could not be effectively utilized and so an efficiency of the ultrasonic vibrator could not be well realized.